Various fluids are used in numerous applications for a variety of purposes, such as actuation of devices. For example, in wellbores, fluids are used to control pressure, move drill cuttings or waste from downhole to the surface, treat different conditions downhole, such as lost circulation, and various other purposes.
When drilling a borehole through subsurface formations, drill cuttings may accumulate in an annular space (“annulus”) between the drill string, including the BHA, and the wall of the borehole. Transport of drill cuttings out of the borehole to the surface is performed by hydraulic drag on the cuttings from the mud as the mud is pumped through the drill string and exits through courses or nozzles on a drill bit at the end of the BHA. The effectiveness of cuttings transport may depend on the mud velocity, mud rheology, borehole inclination, cuttings size and cuttings density. When excessive amounts of cuttings build up in the annulus, the friction on the drill string increases with a corresponding increase of risk of the drill string becoming stuck in the borehole. The rate at which the borehole is drilled may be reduced until the excess cuttings are cleared away by the mud flow.
To help clear away the cuttings from the annulus while maintaining drilling rate, some of the mud flow may be diverted from the interior of the drill string directly to the annulus using a flow diverter. Such mud flow diversion may increase the velocity of the mud in the annulus. Mud having increased velocity in the annulus may provide better cuttings lifting and may clear the excess cuttings from the annulus. The mud flow diverted to the annulus from the drill string, however, may enter the annulus at a high velocity, this may increase the risk of fracturing some exposed subsurface formations and corresponding loss of mud.
Additionally, the mud flow rate through the BHA may be within a certain range for the BHA to function properly. If the mud flow rate is too low, the drilling process may not be performed adequately (such as drill bit cleaning and drilling tool operation). If the mud flow rate is too high, some components of the BHA may be damaged or destroyed. However, the required mud flow rate to ensure proper cuttings transport in the annulus may be too high to be transmitted through the BHA without risk of BHA damage.